Why Do You Care About Fairness? Ask A Chimp

What do you mean you got a grape? I only got a carrot!
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What do you mean you got a grape? I only got a carrot!

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Anyone who has spent time with a child knows the all too familiar refrain: "That's not fair!" But it's not just humans who recognize when they're not getting an equitable share of pie (or toys, or time with Mom and Dad, as the case may be). Some animals, including monkeys, fish and dogs, can also detect inequity.

What we haven't known is whether animals notice when they get favored treatment and will reject a treat to keep things equal. Primate researchers Sarah Brosnan of Georgia State University and Frans de Waal of Emory University say yes — but only some species will.

"The response to getting less than a partner ... is widespread throughout the animal kingdom in species that cooperate," Brosnan tells Shots. "Cooperative species" include primates, some species of fish, and wolf packs, among many others. But the second half of fairness, she adds, is noticing when you get more, and doing something about it to maintain that social relationship.

"This second aspect is something special," Brosnan says. Getting less of something in the short run, in exchange for a social gain — like having a happy partner by your side — is unusual. In fact, only humans and their closest ape cousins seem to do it.

The findings are part of Brosnan and de Waal's broader review of inequity among nonhuman primates and other animals, published Thursday in Science. One study they cite found that when two capuchin monkeys worked together to achieve rewards, if one received a grape and the other a cucumber (less yummy, I'd have to agree), the monkey with the cucumber would toss it away, in apparent anger.

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On the flip side, when two unrelated chimps put side by side were presented with a tasty grape and a less tasty carrot, the chimp with the grape sometimes threw it away. "I would say that the most likely cause was either fear of retribution or just general discomfort about being around an individual getting less than you," says Brosnan. Differences in the social hierarchy also played a role, she says. Dominant chimps were angrier when they were on the receiving end of a lesser reward than those lower in the pecking order.

The results among the chimps are indicative of highly cooperative societies, where relying on someone else is especially crucial. This may be why chimpanzees and humans will avoid inequity, Brosnan suggests, to have long-term cooperation from friends.

However, she cautions against calling it fairness exactly: "Fairness is a social ideal" she says. ... [The animals] don't have social ideals in the same sense [that people do]." Her research reveals behaviors that may look like a push for fairness; but that doesn't mean strategic, higher-order thinking is driving it. The explanation may be much simpler, based more on emotion, Brosnan says: "When my social partner gets upset, I give them something that makes them happy."

If you, too, are the type of person who demands your fair share in life, this may be evolutionarily advantageous. "If that's the kind of person you are, then there's some evidence that you do better in the world," Robert Frank, economist at Cornell's Johnson Graduate School of Management, tells Shots. "People aren't going to strike one-sided bargains with you; they'll know not to mess with you."

So complain on, complainers. Your strict sense of fairness may be doing you good.

Shots is the online channel for health stories from the NPR Science Desk. We report on news that can make a difference for your health and show how policy shapes our health choices. Look to Shots for the latest on research and medical treatments, as well as the business side of health. Your hosts are Scott Hensley and Nancy Shute. You can reach the Shots team via our contact form.